AndyMark Nanotube gearbox issue

[Taylor]

We'd been driving our robot around yesterday when we noticed a couple wheels would stop spinning intermittently. We looked closer and noticed that when we turned the wheels by hand, sometimes it would catch and we'd be unable to turn them except by force.
We're direct-driving mecanum wheels with 1/8" keys from the output shafts of the gearboxes. The wheel is perhaps a quarter inch away from the tube wall - we don't think cantilevered load is an issue.
We took the wheels off and checked the gearboxes. They were all still nicely lubed, there was no discernible wear on the gears; however, we noticed we could push-and-pull the output shaft maybe 3/32" in one gearbox, just barely in another, and the other two held fast. Especially in the gearbox with the "loose" output shaft, we could see the large gear would wobble a bit. We're thinking this wobble may be causing the seizures.
Has anybody done surgery on the nanotube gearing? We don't doubt our ability to take it apart, but putting the gears back in correctly looks to be a tall order, and one we don't want to tackle without necessity. As near as we can tell, the rings and spacers are placed where they're supposed to be - we're not missing any parts from the .stp file.
Any ideas?

[Alex Cormier]

Originally Posted by Taylor

We'd been driving our robot around yesterday when we noticed a couple wheels would stop spinning intermittently. We looked closer and noticed that when we turned the wheels by hand, sometimes it would catch and we'd be unable to turn them except by force.
We're direct-driving mecanum wheels with 1/8" keys from the output shafts of the gearboxes. The wheel is perhaps a quarter inch away from the tube wall - we don't think cantilevered load is an issue.
We took the wheels off and checked the gearboxes. They were all still nicely lubed, there was no discernible wear on the gears; however, we noticed we could push-and-pull the output shaft maybe 3/32" in one gearbox, just barely in another, and the other two held fast. Especially in the gearbox with the "loose" output shaft, we could see the large gear would wobble a bit. We're thinking this wobble may be causing the seizures.
Has anybody done surgery on the nanotube gearing? We don't doubt our ability to take it apart, but putting the gears back in correctly looks to be a tall order, and one we don't want to tackle without necessity. As near as we can tell, the rings and spacers are placed where they're supposed to be - we're not missing any parts from the .stp file.
Any ideas?

I purchased the Gen 1 Shifters. I also have a wobble in a few gears on both transmissions.

[Chris_Elston]

Originally Posted by Taylor

We'd been driving our robot around yesterday when we noticed a couple wheels would stop spinning intermittently.

We had this issue last year:

Our Nanos
http://www.flickr.com/photos/teamthr...7623925567282/

Put two washers between the CIM motor and the Nano gearbox. That fixed it for us, I remember.

Also check this bearing, make sure it is not tilting the CIM one way. If so, change bearing to flush bearing or use the washers to space the CIM out.

[Jonathan Norris]

We put together our nanos the other day and saw some binding. I found two main issues, first we installed the CIMs with two washers before the pinion gear, and it seemed that when we had the gearbox upside-down the first stage large gear had enough slop in it to bind with one of those washers, we removed one of the washers to solve that problem. Then we still saw a little binding, I noticed that when I loosened the CIM screws a bit there was a good amount of movement in the CIM mount, I pulled the CIMs away from the other stage before tightening it's screws and that got rid of all the binding. They defiantly take a bit of working in, also make sure that you grease your gearboxes... the number of teams I've seen without greased gearboxes...

[Kevin Sevcik]

We had this issue as well, but I don't think it was the CIM's fault. I wish I had a nano in front of me cause then I could definitively tell you exactly what to do. I do know that it was caused by lack of spacing between the large output gear and the large cluster gear. Ithink we caused this by putting the small flanged FR-6-zz-hex bearing in backwards. This is the hex hole bearing on the cluster gear shaft. The flange goes on the inside of the gearbox. Then the two button screws tighten down to take up slack on the inside and leave the hex bearing flush with the exterior.

If you put this in backwards with the flange on the outside, things don't stackup properly on the shaft and you get excessive play. If you put it together right and your cluster gears still have play, then you could add a washer or two between the small cluster gear and the hex bearing to push things farther from the output gear.